| On last day of menstruation.
Percent. 35.55 25.49
First twelve days after beginning of menstruation.
Percent. 88.44 70.98
First seven days after end of menstruation.
Per cent. 88.88 70.58
Similar figures are given by Issmer.
Time of copulation.
First week of menstrual period . . Second week of menstrual period Third week of menstrual period. Fourth week of menstrual period
Average duration of pregnancy.
277 days 279 days 287 days 285 days
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